This specification relates to micro-mirror display devices.
Micro-mirror display devices are commonly used in projection displays. These projection displays project light corresponding to color channels of the image. A micro-mirror display device displays the pixels of an image by tilting mirror plates to project light (to display the pixel) or to deflect light (to not display the pixel). The amount of time that the mirror plates are turned on and off controls the intensity for a given pixel and a given color.
The mirror plates are tilted using digital control signals derived from bit plane data for the image. Electrical signals corresponding to the digital control signals for each mirror plate are provided to two electrodes placed on opposite sides of a hinge for the mirror plate. A voltage is applied to the mirror plate, and electrostatic force attraction causes the mirror plate to tilt in one direction or another, depending on the voltage provided to the electrodes. At appropriate times, the micro-mirror display device resets the mirror plates by modifying the voltage applied to the mirror plate. This reset causes the mirror plate to change into a new state, or stay in its current state, as appropriate.
In order to overcome the electrostatic forces on the mirror plate, and thus guarantee a proper mirror plate reset, many micro-mirror display devices use a bipolar reset signal. The bipolar reset signal temporarily applies a negative voltage to the mirror plate during reset. However, a bipolar reset signal can have several problems. For example, the positive and negative power supplies required to generate a bipolar reset signal can be more expensive than positive-only power supplies and generating a negative voltage require more power than generating a non-negative voltage.